2 genes are on different chromosomes
Ex. Seed color and seed texture genes of a pea plant
The genes segregate independently of one another
Law of Independent Assortment
Genes that reside on the same chromosome and this cannot segregate independently
Linked genes or linkage groups
Genes that are linked are usually…?
Inherited together
Ex. Blond hair + Blue eyes
Homologous chromosomes can exchange corresponding segments during…?
Propose 1 of meiosis
crossing over
Further apart on the same chromosome genes are the most likely they are to separate
Recombination
Crossing over results in?
Genetic recombination
Progeny resulting from crossing over appear in repeatable proportions
Recombinant Frequency
Recombinant frequencies for many pairs of linked genes can be used to create..?
Shows arrangement of genes along the chromosome
Genetic Map
To measure distances between genes, scientists use?
Map units
One map unit corresponds to?
A recombination frequency of 0.01
Referred to as a centimorgan (cM)
Greater the distance between 2 genes on a chromosome
The more places between the genes that the chromosome can break
More likely the 2 genes will cross over during synapsis
Recombination frequencies are used to give a?
Picture of the arrangement of genes on a chromosome
A chromosome map created in this fashion
Portrayal of the sequence of genes on a chromosome
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Linkage map
In the normal process of meiosis, chromosomes pair at the metaphase plate and..?
Subsequently separate and migrate to opposite poles
When non disjunction occurs, the chromosomes do not properly separate. Instead..?
Both members of one homologous chromosome pair migrate to same pole
As a result of non disjunction..?
Half the gametes will have an extra chromosome and half will be missing a chromosome
Single, unpaired chromosome
Monosomy
Having 3 chromosomes
Trisomy
Gametes with missing or with extra chromosomes are usually?
Sterile
Sometimes chromosome imbalances are?
These almost always lead to..?
Fertile
Genetic defects
Most chromosome abnormalities are..?
Lethal and cause spontaneous abortion of the embryo
What occurs when hen an egg or sperm with an extra chromosome 21 chromosomes fuses with a normal gamete?
Down Syndrome
Down syndrome results in a zygote with?
3 copies of chromosome 21
Trisomy 21
Down Syndrome individuals bear various abnormalities such as…?
Mental retardation, heart defects, respiratory problems, and deformities in external features
Results when there is non disjunction of the sex chromosomes
Turner Syndrome
Individuals with Turner Syndrome are…?
Physically and sterile
Genetic defects can be caused by…?
Inheritance of an allele (Such as in hemophilia)
Or caused by chromosomal abnormalities
Chromosomal abnormalities result when the inherited genome is missing a chromosome or has an extra chromosome or when one or more chromosomes have portions…?
Deleted (Deletion)
Duplicated (Duplication)
Move to another chromosome (Translocation)
Rearranged in reverse orientation on the same chromosome (Inversion)
Autosomal Recessive
Inability to properly break down the amino acid phenylalanine
Causes mental retardation
Phenylkentonuria (PKU)
Autosomal Recessive
Abnormal hemoglobin
Red blood cells are unable to effectively transport oxygen throughout the body
Sickle-cell anemia
Autosomal Recessive
Inability to properly break down certain lipids
Accumulation of the lipids in brain cells causes progressive nervous system dysfunction and is usually fatal by age 4
Tay-Sachs Disease
Autosomal Dominant
Expression begins in middle age
Mild mental illness and loss of motor control
Total physical and mental incapability
Huntington’s Disease
Sex-linked Recessive
Inability to code for a clotting factor required to form normal blood clots
Hemophilia
Sex-linked Recessive
Inability to distinguish red from green
Red-Green Color Blindness
Sex-linked Dominant
Absence of an essential muscle protein
Dystrophy deteriorating muscles and loss of coordinantion
Duchenne’s Muscular
Nondisjunction of chromosome 21
Trisomy 21
Physical abnormalities
Mental retardation
Down Syndrome
Nondisjunction of sex chromosomes
XO and female
Union of a gamete missing the sex chromosome with a normal egg or sperm bearing an X chromosome
Turner Syndrome
Nondisjunction of sex chromosomes
XXY and male
Union of XX gamete and normal Y gamete
Sterile and often mentally retarded
Klinefelter Syndrome
Deletion in chromosome 5
Physical and mental retardation and catlike cry
Cri Du Chat Syndrome
Non-Nuclear Inheritance
Mitochondria, Chloroplasts, and other plastids possess?
Small amount of DNA
Non-Nuclear Inheritance
Some of these gametes are important for?
Organelle assembly and function
Non-Nuclear Inheritance
A cell is highly_____for organelle genes
Polyploid
Organelle genes tend to mutate at a ____rate
Faster
